feat: Add frontend support for `min_tokens` and `ignore_eos` (outside of...

feat: Add frontend support for `min_tokens` and `ignore_eos` (outside of `nvext`) and Structured Output / Guided Decoding (#2380)
Signed-off-by: KrishnanPrash <140860868+KrishnanPrash@users.noreply.github.com>
Co-authored-by: Ryan McCormick <rmccormick@nvidia.com>
Co-authored-by: Ayush Agarwal <ayushag@nvidia.com>

lib/llm/src/entrypoint/input/batch.rs

@@ -222,7 +222,11 @@ async fn evaluate(
         )
         .temperature(template.as_ref().map_or(0.7, |t| t.temperature))
         .build()?;
-    let req = NvCreateChatCompletionRequest { inner, nvext: None };
+    let req = NvCreateChatCompletionRequest {
+        inner,
+        common: Default::default(),
+        nvext: None,
+    };
     let mut stream = engine.generate(Context::new(req)).await?;
     let mut output = String::new();
     while let Some(item) = stream.next().await {

lib/llm/src/entrypoint/input/text.rs

@@ -118,6 +118,7 @@ async fn main_loop(
 
         let req = NvCreateChatCompletionRequest {
             inner,
+            common: Default::default(),
             nvext: Some(nvext),
         };
 

lib/llm/src/http/service/openai.rs

@@ -1237,6 +1237,7 @@ mod tests {
                 messages: vec![],
                 ..Default::default()
             },
+            common: Default::default(),
             nvext: None,
         };
         let result = validate_chat_completion_required_fields(&request);
@@ -1263,6 +1264,7 @@ mod tests {
                 )],
                 ..Default::default()
             },
+            common: Default::default(),
             nvext: None,
         };
         let result = validate_chat_completion_required_fields(&request);

lib/llm/src/protocols/openai.rs

@@ -20,8 +20,10 @@ use super::{
     common::{self, SamplingOptionsProvider, StopConditionsProvider},
     ContentProvider,
 };
+use crate::protocols::openai::common_ext::CommonExtProvider;
 
 pub mod chat_completions;
+pub mod common_ext;
 pub mod completions;
 pub mod embeddings;
 pub mod models;
@@ -61,9 +63,23 @@ trait OpenAIStopConditionsProvider {
     fn get_stop(&self) -> Option<Vec<String>>;
 
     fn nvext(&self) -> Option<&nvext::NvExt>;
+
+    /// Get ignore_eos from CommonExt if the type supports it.
+    /// Default returns None for types without CommonExt support.
+    fn get_common_ignore_eos(&self) -> Option<bool> {
+        None
+    }
+
+    /// Get the effective ignore_eos value, considering both CommonExt and NvExt.
+    /// CommonExt (root-level) takes precedence over NvExt.
+    fn get_ignore_eos(&self) -> Option<bool> {
+        // Check common first (takes precedence), then fall back to nvext
+        self.get_common_ignore_eos()
+            .or_else(|| self.nvext().and_then(|nv| nv.ignore_eos))
+    }
 }
 
-impl<T: OpenAISamplingOptionsProvider> SamplingOptionsProvider for T {
+impl<T: OpenAISamplingOptionsProvider + CommonExtProvider> SamplingOptionsProvider for T {
     fn extract_sampling_options(&self) -> Result<common::SamplingOptions> {
         // let result = self.validate();
         // if let Err(e) = result {
@@ -88,29 +104,26 @@ impl<T: OpenAISamplingOptionsProvider> SamplingOptionsProvider for T {
             }
         }
 
-        let mut guided_decoding = None;
-        if let Some(nvext) = self.nvext() {
-            let guided_decoding_backend = nvext.guided_decoding_backend.clone();
-            let guided_json = nvext.guided_json.clone();
-            let guided_regex = nvext.guided_regex.clone();
-            let guided_grammar = nvext.guided_grammar.clone();
-            let guided_choice = nvext.guided_choice.clone();
-
-            match common::GuidedDecodingOptions::from_optional(
-                guided_json,
+        let guided_decoding_backend = self.get_guided_decoding_backend();
+        let guided_json = self.get_guided_json();
+        let guided_regex = self.get_guided_regex();
+        let guided_grammar = self.get_guided_grammar();
+        let guided_choice = self.get_guided_choice();
+
+        let guided_decoding = match common::GuidedDecodingOptions::from_optional(
+            guided_json.cloned(),
             guided_regex,
             guided_choice,
             guided_grammar,
             guided_decoding_backend,
         ) {
-                Ok(options) => guided_decoding = options,
+            Ok(options) => options,
             Err(e) => {
                 // Handle the validation error (log, return error, etc.)
-                    tracing::error!("Invalid guided decoding options: {}", e);
+                tracing::error!("Invalid guided decoding options: {:?}", e);
                 return Err(e);
             }
-            }
-        }
+        };
 
         Ok(common::SamplingOptions {
             n: None,
@@ -142,11 +155,8 @@ impl<T: OpenAIStopConditionsProvider> StopConditionsProvider for T {
             }
         }
 
-        let mut ignore_eos = None;
-
-        if let Some(nvext) = self.nvext() {
-            ignore_eos = nvext.ignore_eos;
-        }
+        // Use the trait method to get ignore_eos, which handles precedence
+        let ignore_eos = self.get_ignore_eos();
 
         Ok(common::StopConditions {
             max_tokens,

lib/llm/src/protocols/openai/chat_completions.rs

@@ -20,8 +20,10 @@ use validator::Validate;
 use crate::engines::ValidateRequest;
 
 use super::{
-    nvext::NvExt, nvext::NvExtProvider, validate, OpenAISamplingOptionsProvider,
-    OpenAIStopConditionsProvider,
+    common_ext::{CommonExt, CommonExtProvider},
+    nvext::NvExt,
+    nvext::NvExtProvider,
+    validate, OpenAISamplingOptionsProvider, OpenAIStopConditionsProvider,
 };
 
 mod aggregator;
@@ -31,17 +33,21 @@ pub use aggregator::DeltaAggregator;
 pub use delta::DeltaGenerator;
 
 /// A request structure for creating a chat completion, extending OpenAI's
-/// `CreateChatCompletionRequest` with [`NvExt`] extensions.
+/// `CreateChatCompletionRequest` with [`NvExt`] extensions and common fields.
 ///
 /// # Fields
 /// - `inner`: The base OpenAI chat completion request, embedded using `serde(flatten)`.
-/// - `nvext`: The optional NVIDIA extension field. See [`NvExt`] for
-///   more details.
+/// - `common`: Common extension fields (ignore_eos, min_tokens) at root level, embedded using `serde(flatten)`.
+/// - `nvext`: The optional NVIDIA extension field. See [`NvExt`] for more details.
+///   Note: If ignore_eos is specified in both common and nvext, the common (root-level) value takes precedence.
 #[derive(Serialize, Deserialize, Validate, Debug, Clone)]
 pub struct NvCreateChatCompletionRequest {
     #[serde(flatten)]
     pub inner: async_openai::types::CreateChatCompletionRequest,
 
+    #[serde(flatten, default)]
+    pub common: CommonExt,
+
     #[serde(skip_serializing_if = "Option::is_none")]
     pub nvext: Option<NvExt>,
 }
@@ -139,6 +145,52 @@ impl OpenAISamplingOptionsProvider for NvCreateChatCompletionRequest {
     }
 }
 
+/// Implements `CommonExtProvider` for `NvCreateChatCompletionRequest`,
+/// providing access to common extension fields.
+impl CommonExtProvider for NvCreateChatCompletionRequest {
+    /// Returns a reference to the CommonExt struct.
+    fn common_ext(&self) -> Option<&CommonExt> {
+        Some(&self.common)
+    }
+
+    /// Guided Decoding Options
+    fn get_guided_json(&self) -> Option<&serde_json::Value> {
+        self.common
+            .guided_json
+            .as_ref()
+            .or_else(|| self.nvext.as_ref().and_then(|nv| nv.guided_json.as_ref()))
+    }
+
+    fn get_guided_regex(&self) -> Option<String> {
+        self.common
+            .guided_regex
+            .clone()
+            .or_else(|| self.nvext.as_ref().and_then(|nv| nv.guided_regex.clone()))
+    }
+
+    fn get_guided_grammar(&self) -> Option<String> {
+        self.common
+            .guided_grammar
+            .clone()
+            .or_else(|| self.nvext.as_ref().and_then(|nv| nv.guided_grammar.clone()))
+    }
+
+    fn get_guided_choice(&self) -> Option<Vec<String>> {
+        self.common
+            .guided_choice
+            .clone()
+            .or_else(|| self.nvext.as_ref().and_then(|nv| nv.guided_choice.clone()))
+    }
+
+    fn get_guided_decoding_backend(&self) -> Option<String> {
+        self.common.guided_decoding_backend.clone().or_else(|| {
+            self.nvext
+                .as_ref()
+                .and_then(|nv| nv.guided_decoding_backend.clone())
+        })
+    }
+}
+
 /// Implements `OpenAIStopConditionsProvider` for `NvCreateChatCompletionRequest`,
 /// providing access to stop conditions that control chat completion behavior.
 impl OpenAIStopConditionsProvider for NvCreateChatCompletionRequest {
@@ -149,12 +201,10 @@ impl OpenAIStopConditionsProvider for NvCreateChatCompletionRequest {
     }
 
     /// Retrieves the minimum number of tokens required in the response.
-    ///
-    /// # Note
-    /// This method is currently a placeholder and always returns `None`
-    /// since `min_tokens` is not an OpenAI-supported parameter.
+    /// Returns `min_tokens` Value
+    /// `min_tokens` is not an OpenAI-supported parameter.
     fn get_min_tokens(&self) -> Option<u32> {
-        None
+        self.common.min_tokens
     }
 
     /// Retrieves the stop conditions that terminate the chat completion response.
@@ -175,6 +225,11 @@ impl OpenAIStopConditionsProvider for NvCreateChatCompletionRequest {
     fn nvext(&self) -> Option<&NvExt> {
         self.nvext.as_ref()
     }
+
+    /// Get ignore_eos from CommonExt.
+    fn get_common_ignore_eos(&self) -> Option<bool> {
+        self.common.ignore_eos
+    }
 }
 
 /// Implements `ValidateRequest` for `NvCreateChatCompletionRequest`,

lib/llm/src/protocols/openai/common_ext.rs

+// SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use derive_builder::Builder;
+use serde::{Deserialize, Serialize};
+use validator::Validate;
+
+/// Common extensions for OpenAI API requests that are not part of the standard OpenAI spec
+/// but are commonly needed across different request types.
+#[derive(Serialize, Deserialize, Builder, Validate, Debug, Clone, Default)]
+pub struct CommonExt {
+    /// If true, the model will ignore the end of string token and generate to max_tokens.
+    /// This field can also be specified in nvext, but the root-level value takes precedence.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[builder(default, setter(strip_option))]
+    pub ignore_eos: Option<bool>,
+
+    /// The minimum number of tokens to generate.
+    /// This is a common parameter needed across different request types.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[builder(default, setter(strip_option))]
+    pub min_tokens: Option<u32>,
+
+    /// Guided Decoding Options
+    /// If specified, the output will be a JSON object. Can be a string, an object, or null.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[builder(default, setter(strip_option))]
+    pub guided_json: Option<serde_json::Value>,
+
+    /// If specified, the output will follow the regex pattern. Can be a string or null.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[builder(default, setter(strip_option))]
+    pub guided_regex: Option<String>,
+
+    /// If specified, the output will follow the context-free grammar. Can be a string or null.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[builder(default, setter(strip_option))]
+    pub guided_grammar: Option<String>,
+
+    /// If specified, the output will be exactly one of the choices.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[builder(default, setter(strip_option))]
+    pub guided_choice: Option<Vec<String>>,
+
+    /// If specified, the backend to use for guided decoding, can be backends like xgrammar or custom guided decoding backend
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[builder(default, setter(strip_option))]
+    pub guided_decoding_backend: Option<String>,
+}
+
+impl CommonExt {
+    pub fn builder() -> CommonExtBuilder {
+        CommonExtBuilder::default()
+    }
+}
+
+/// Trait for types that provide CommonExt fields
+pub trait CommonExtProvider {
+    /// Get a reference to the CommonExt struct if available
+    fn common_ext(&self) -> Option<&CommonExt>;
+
+    /// Guided Decoding Options
+    fn get_guided_json(&self) -> Option<&serde_json::Value>;
+    fn get_guided_regex(&self) -> Option<String>;
+    fn get_guided_grammar(&self) -> Option<String>;
+    fn get_guided_choice(&self) -> Option<Vec<String>>;
+    fn get_guided_decoding_backend(&self) -> Option<String>;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use serde_json;
+
+    #[test]
+    fn test_common_ext_builder_default() {
+        let common_ext = CommonExt::builder().build().unwrap();
+        assert_eq!(common_ext.ignore_eos, None);
+        assert_eq!(common_ext.min_tokens, None);
+        assert_eq!(common_ext.guided_json, None);
+        assert_eq!(common_ext.guided_regex, None);
+        assert_eq!(common_ext.guided_grammar, None);
+        assert_eq!(common_ext.guided_choice, None);
+        assert_eq!(common_ext.guided_decoding_backend, None);
+    }
+
+    #[test]
+    fn test_common_ext_builder_with_values() {
+        let common_ext = CommonExt::builder()
+            .ignore_eos(true)
+            .min_tokens(10)
+            .guided_json(serde_json::json!({"key": "value"}))
+            .guided_regex("regex".to_string())
+            .guided_grammar("grammar".to_string())
+            .guided_choice(vec!["choice1".to_string(), "choice2".to_string()])
+            .guided_decoding_backend("backend".to_string())
+            .build()
+            .unwrap();
+
+        assert_eq!(common_ext.ignore_eos, Some(true));
+        assert_eq!(common_ext.min_tokens, Some(10));
+        assert_eq!(
+            common_ext.guided_json.as_ref(),
+            Some(&serde_json::json!({"key": "value"}))
+        );
+        assert_eq!(common_ext.guided_regex, Some("regex".to_string()));
+        assert_eq!(common_ext.guided_grammar, Some("grammar".to_string()));
+        assert_eq!(
+            common_ext.guided_choice,
+            Some(vec!["choice1".to_string(), "choice2".to_string()])
+        );
+        assert_eq!(
+            common_ext.guided_decoding_backend,
+            Some("backend".to_string())
+        );
+    }
+
+    #[test]
+    fn test_common_ext_fields() {
+        // Test that CommonExt fields can be set and retrieved correctly
+        let common_ext = CommonExt::builder()
+            .ignore_eos(false)
+            .min_tokens(5)
+            .build()
+            .unwrap();
+
+        assert_eq!(common_ext.ignore_eos, Some(false));
+        assert_eq!(common_ext.min_tokens, Some(5));
+    }
+
+    #[test]
+    fn test_validation_min_tokens() {
+        // Test that min_tokens with 0 is valid
+        let common_ext = CommonExt {
+            ignore_eos: None,
+            min_tokens: Some(0), // Should be valid (min = 0)
+            guided_json: None,
+            guided_regex: None,
+            guided_grammar: None,
+            guided_choice: None,
+            guided_decoding_backend: None,
+        };
+        assert!(common_ext.validate().is_ok());
+    }
+
+    #[test]
+    fn test_common_ext_neither_specified() {
+        // Test that neither ignore_eos nor min_tokens specified works
+        let common_ext = CommonExt::builder().build().unwrap();
+
+        assert_eq!(common_ext.ignore_eos, None);
+        assert_eq!(common_ext.min_tokens, None);
+        assert!(common_ext.validate().is_ok());
+    }
+
+    #[test]
+    fn test_common_ext_default() {
+        // Test that Default trait implementation works correctly
+        let common_ext = CommonExt::default();
+
+        assert_eq!(common_ext.ignore_eos, None);
+        assert_eq!(common_ext.min_tokens, None);
+        assert!(common_ext.validate().is_ok());
+    }
+}

lib/llm/src/protocols/openai/completions.rs

@@ -22,6 +22,7 @@ use crate::engines::ValidateRequest;
 
 use super::{
     common::{self, SamplingOptionsProvider, StopConditionsProvider},
+    common_ext::{CommonExt, CommonExtProvider},
     nvext::{NvExt, NvExtProvider},
     validate, ContentProvider, OpenAISamplingOptionsProvider, OpenAIStopConditionsProvider,
 };
@@ -37,6 +38,9 @@ pub struct NvCreateCompletionRequest {
     #[serde(flatten)]
     pub inner: async_openai::types::CreateCompletionRequest,
 
+    #[serde(flatten)]
+    pub common: CommonExt,
+
     #[serde(skip_serializing_if = "Option::is_none")]
     pub nvext: Option<NvExt>,
 }
@@ -131,13 +135,56 @@ impl OpenAISamplingOptionsProvider for NvCreateCompletionRequest {
     }
 }
 
+impl CommonExtProvider for NvCreateCompletionRequest {
+    fn common_ext(&self) -> Option<&CommonExt> {
+        Some(&self.common)
+    }
+
+    /// Guided Decoding Options
+    fn get_guided_json(&self) -> Option<&serde_json::Value> {
+        self.common
+            .guided_json
+            .as_ref()
+            .or_else(|| self.nvext.as_ref().and_then(|nv| nv.guided_json.as_ref()))
+    }
+
+    fn get_guided_regex(&self) -> Option<String> {
+        self.common
+            .guided_regex
+            .clone()
+            .or_else(|| self.nvext.as_ref().and_then(|nv| nv.guided_regex.clone()))
+    }
+
+    fn get_guided_grammar(&self) -> Option<String> {
+        self.common
+            .guided_grammar
+            .clone()
+            .or_else(|| self.nvext.as_ref().and_then(|nv| nv.guided_grammar.clone()))
+    }
+
+    fn get_guided_choice(&self) -> Option<Vec<String>> {
+        self.common
+            .guided_choice
+            .clone()
+            .or_else(|| self.nvext.as_ref().and_then(|nv| nv.guided_choice.clone()))
+    }
+
+    fn get_guided_decoding_backend(&self) -> Option<String> {
+        self.common.guided_decoding_backend.clone().or_else(|| {
+            self.nvext
+                .as_ref()
+                .and_then(|nv| nv.guided_decoding_backend.clone())
+        })
+    }
+}
+
 impl OpenAIStopConditionsProvider for NvCreateCompletionRequest {
     fn get_max_tokens(&self) -> Option<u32> {
         self.inner.max_tokens
     }
 
     fn get_min_tokens(&self) -> Option<u32> {
-        None
+        self.common.min_tokens
     }
 
     fn get_stop(&self) -> Option<Vec<String>> {
@@ -147,6 +194,10 @@ impl OpenAIStopConditionsProvider for NvCreateCompletionRequest {
     fn nvext(&self) -> Option<&NvExt> {
         self.nvext.as_ref()
     }
+
+    fn get_common_ignore_eos(&self) -> Option<bool> {
+        self.common.ignore_eos
+    }
 }
 
 #[derive(Builder)]

lib/llm/src/protocols/openai/responses.rs

@@ -185,6 +185,7 @@ impl TryFrom<NvCreateResponse> for NvCreateChatCompletionRequest {
                 stream: Some(true), // Set this to Some(True) by default to aggregate stream
                 ..Default::default()
             },
+            common: Default::default(),
             nvext: resp.nvext,
         })
     }

lib/llm/tests/http-service.rs

@@ -765,6 +765,7 @@ async fn test_nv_custom_client(
 
     let request = NvCreateChatCompletionRequest {
         inner: inner_request,
+        common: Default::default(),
         nvext: None,
     };
 
@@ -802,6 +803,7 @@ async fn test_nv_custom_client(
 
     let request = NvCreateChatCompletionRequest {
         inner: inner_request,
+        common: Default::default(),
         nvext: None,
     };
 
@@ -840,6 +842,7 @@ async fn test_nv_custom_client(
 
     let request = NvCreateChatCompletionRequest {
         inner: inner_request,
+        common: Default::default(),
         nvext: None,
     };
 

lib/llm/tests/openai_completions.rs

@@ -36,7 +36,11 @@ impl CompletionSample {
 
         let inner = builder.build().unwrap();
 
-        let request = NvCreateCompletionRequest { inner, nvext: None };
+        let request = NvCreateCompletionRequest {
+            inner,
+            common: Default::default(),
+            nvext: None,
+        };
 
         Ok(Self {
             request,

lib/llm/tests/preprocessor.rs

@@ -266,7 +266,11 @@ impl Request {
         }
         let inner = inner.build().unwrap();
 
-        NvCreateChatCompletionRequest { inner, nvext: None }
+        NvCreateChatCompletionRequest {
+            inner,
+            common: Default::default(),
+            nvext: None,
+        }
     }
 }
 

lib/llm/tests/test_common_ext.rs

+// SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use dynamo_llm::protocols::{
+    common::StopConditionsProvider,
+    openai::{
+        chat_completions::NvCreateChatCompletionRequest,
+        common_ext::{CommonExt, CommonExtProvider},
+        completions::NvCreateCompletionRequest,
+        nvext::NvExt,
+    },
+};
+
+#[test]
+fn test_chat_completions_ignore_eos_from_common() {
+    // Test that ignore_eos can be specified at root level
+    let json_str = r#"{
+        "model": "test-model",
+        "messages": [{"role": "user", "content": "Hello"}],
+        "ignore_eos": true,
+        "min_tokens": 100
+    }"#;
+
+    let request: NvCreateChatCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(request.common.ignore_eos, Some(true));
+    assert_eq!(request.common.min_tokens, Some(100));
+}
+
+#[test]
+fn test_chat_completions_guided_decoding_from_common() {
+    // Test that guided_json can be specified at root level
+    let json_str = r#"{
+        "model": "test-model",
+        "messages": [{"role": "user", "content": "Hello"}],
+        "guided_json": {"key": "value"}
+    }"#;
+
+    let request: NvCreateChatCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(
+        request.common.guided_json,
+        Some(serde_json::json!({"key": "value"}))
+    );
+    assert_eq!(
+        request.get_guided_json(),
+        Some(&serde_json::json!({"key": "value"}))
+    );
+
+    // Test guided_regex can be specified at root level
+    let json_str = r#"{
+        "model": "test-model",
+        "messages": [{"role": "user", "content": "Hello"}],
+        "guided_regex": "*"
+    }"#;
+
+    let request: NvCreateChatCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(request.common.guided_regex, Some("*".to_string()));
+    assert_eq!(request.get_guided_regex(), Some("*".to_string()));
+
+    // Test guided_grammar can be specified at root level
+    let json_str = r#"{
+        "model": "test-model",
+        "messages": [{"role": "user", "content": "Hello"}],
+        "guided_grammar": "::=[1-9]"
+    }"#;
+
+    let request: NvCreateChatCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(request.common.guided_grammar, Some("::=[1-9]".to_string()));
+    assert_eq!(request.get_guided_grammar(), Some("::=[1-9]".to_string()));
+
+    // Test guided_choice can be specified at root level
+    let json_str = r#"{
+        "model": "test-model",
+        "messages": [{"role": "user", "content": "Hello"}],
+        "guided_choice": ["choice1", "choice2"]
+    }"#;
+
+    let request: NvCreateChatCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(
+        request.common.guided_choice,
+        Some(vec!["choice1".to_string(), "choice2".to_string()])
+    );
+    assert_eq!(
+        request.get_guided_choice(),
+        Some(vec!["choice1".to_string(), "choice2".to_string()])
+    );
+
+    // Test guided_decoding_backend can be specified at root level
+    let json_str = r#"{
+        "model": "test-model",
+        "messages": [{"role": "user", "content": "Hello"}],
+        "guided_decoding_backend": "backend"
+    }"#;
+
+    let request: NvCreateChatCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(
+        request.common.guided_decoding_backend,
+        Some("backend".to_string())
+    );
+    assert_eq!(
+        request.get_guided_decoding_backend(),
+        Some("backend".to_string())
+    );
+}
+
+#[test]
+fn test_chat_completions_common_overrides_nvext() {
+    // Test that root-level ignore_eos overrides nvext ignore_eos
+    let json_str = r#"{
+        "model": "test-model",
+        "messages": [{"role": "user", "content": "Hello"}],
+        "ignore_eos": false,
+        "guided_regex": ".*",
+        "min_tokens": 50,
+        "nvext": {
+            "ignore_eos": true,
+            "guided_regex": "./*"
+        }
+    }"#;
+
+    let request: NvCreateChatCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(request.common.ignore_eos, Some(false));
+    assert_eq!(request.common.guided_regex, Some(".*".to_string()));
+    assert_eq!(
+        request.nvext.as_ref().and_then(|nv| nv.ignore_eos),
+        Some(true)
+    );
+    assert_eq!(request.get_guided_regex(), Some(".*".to_string())); // common value takes precedence
+                                                                    // Verify precedence through stop conditions extraction
+    let stop_conditions = request.extract_stop_conditions().unwrap();
+    assert_eq!(stop_conditions.ignore_eos, Some(false)); // common value takes precedence
+    assert_eq!(stop_conditions.min_tokens, Some(50));
+}
+
+#[test]
+fn test_chat_completions_backward_compatibility() {
+    // Test backward compatibility - ignore_eos and guided_json only in nvext
+    let json_str = r#"{
+        "model": "test-model",
+        "messages": [{"role": "user", "content": "Hello"}],
+        "nvext": {
+            "ignore_eos": true,
+            "guided_json": {"key": "value"}
+        }
+    }"#;
+
+    let request: NvCreateChatCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(request.common.ignore_eos, None);
+    assert_eq!(request.common.guided_json, None);
+    assert_eq!(
+        request.nvext.as_ref().and_then(|nv| nv.ignore_eos),
+        Some(true)
+    );
+    assert_eq!(
+        request
+            .nvext
+            .as_ref()
+            .and_then(|nv| nv.guided_json.as_ref()),
+        Some(&serde_json::json!({"key": "value"}))
+    );
+    assert_eq!(
+        request.get_guided_json(),
+        Some(&serde_json::json!({"key": "value"}))
+    );
+    // Verify through stop conditions extraction
+    let stop_conditions = request.extract_stop_conditions().unwrap();
+    assert_eq!(stop_conditions.ignore_eos, Some(true));
+    assert_eq!(stop_conditions.min_tokens, None);
+}
+
+#[test]
+fn test_completions_ignore_eos_from_common() {
+    // Test that ignore_eos can be specified at root level for completions
+    let json_str = r#"{
+        "model": "test-model",
+        "prompt": "Hello world",
+        "ignore_eos": true,
+        "min_tokens": 200
+    }"#;
+
+    let request: NvCreateCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(request.common.ignore_eos, Some(true));
+    assert_eq!(request.common.min_tokens, Some(200));
+
+    // Verify through stop conditions extraction
+    let stop_conditions = request.extract_stop_conditions().unwrap();
+    assert_eq!(stop_conditions.ignore_eos, Some(true));
+    assert_eq!(stop_conditions.min_tokens, Some(200));
+}
+
+#[test]
+fn test_completions_common_overrides_nvext() {
+    // Test that root-level ignore_eos overrides nvext ignore_eos for completions
+    let json_str = r#"{
+        "model": "test-model",
+        "prompt": "Hello world",
+        "ignore_eos": false,
+        "min_tokens": 75,
+        "nvext": {
+            "ignore_eos": true
+        }
+    }"#;
+
+    let request: NvCreateCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(request.common.ignore_eos, Some(false));
+    assert_eq!(
+        request.nvext.as_ref().and_then(|nv| nv.ignore_eos),
+        Some(true)
+    );
+    // Verify precedence through stop conditions extraction
+    let stop_conditions = request.extract_stop_conditions().unwrap();
+    assert_eq!(stop_conditions.ignore_eos, Some(false)); // common value takes precedence
+    assert_eq!(stop_conditions.min_tokens, Some(75));
+}
+
+#[test]
+fn test_serialization_preserves_structure() {
+    // Test that serialization preserves the flattened structure
+    let request = NvCreateChatCompletionRequest {
+        inner: async_openai::types::CreateChatCompletionRequest {
+            model: "test-model".to_string(),
+            messages: vec![async_openai::types::ChatCompletionRequestMessage::User(
+                async_openai::types::ChatCompletionRequestUserMessage {
+                    content: async_openai::types::ChatCompletionRequestUserMessageContent::Text(
+                        "Hello".to_string(),
+                    ),
+                    ..Default::default()
+                },
+            )],
+            ..Default::default()
+        },
+        common: CommonExt {
+            ignore_eos: Some(true),
+            min_tokens: Some(100),
+            ..Default::default()
+        },
+        nvext: Some(NvExt {
+            ignore_eos: Some(false),
+            ..Default::default()
+        }),
+    };
+
+    let json = serde_json::to_value(&request).unwrap();
+
+    // Check that fields are at the expected levels
+    assert_eq!(json["model"], "test-model");
+    assert_eq!(json["ignore_eos"], true); // From common (flattened)
+    assert_eq!(json["min_tokens"], 100); // From common (flattened)
+    assert_eq!(json["nvext"]["ignore_eos"], false); // From nvext
+
+    // Verify precedence through stop conditions extraction
+    let stop_conditions = request.extract_stop_conditions().unwrap();
+    assert_eq!(stop_conditions.ignore_eos, Some(true)); // common overrides nvext
+    assert_eq!(stop_conditions.min_tokens, Some(100));
+}
+
+#[test]
+fn test_min_tokens_only_at_root_level() {
+    // Test that min_tokens is only available at root level, not in nvext
+    let json_str = r#"{
+        "model": "test-model",
+        "messages": [{"role": "user", "content": "Hello"}],
+        "min_tokens": 150
+    }"#;
+
+    let request: NvCreateChatCompletionRequest = serde_json::from_str(json_str).unwrap();
+
+    assert_eq!(request.common.min_tokens, Some(150));
+
+    // Verify through stop conditions extraction
+    let stop_conditions = request.extract_stop_conditions().unwrap();
+    assert_eq!(stop_conditions.min_tokens, Some(150));
+}